Experimental study and modeling of polymer granular structures submitted to internal underpressure

The paper deals with a system that consists of a granular material encapsulated in a tight, flexible envelope and submitted to an internal underpressure using a vacuum pump. It is found that the underpressure value has a considerable impact on the behavior and properties of the medium. Experimental studies and modeling of this phenomenon are provided in this work. Results of uniaxial tensile tests carried out on special cylindrical samples and characteristic hardening curves are presented for structures filled up with plastic grains. The nonlinear behavior of these materials is modeled using the viscoplastic constitutive Chaboche law, that requires the determination of several material parameters. The parameters identification problem is formulated as an optimization problem and solved by using an evolutionary algorithm. The numerically simulated graphs follow the experimental curves well. A modified version of Chaboche model, capable of capturing the polymer granular structure response to external loading and including underpressure parameter, is proposed. The presented methodology can be easily adapted to other constitutive models and experiments of special granular structures submitted to internal underpressure.

► Unique experimental results for ABS special granular structures are presented in the paper. ► Uniaxial response of granular structures submitted to internal underpressure and uniaxial loading is modeled. ► The classical Chaboche’s model is modified to describe behavior of special granular structures. ► Parameters of the model are identified using evolutionary algorithms on the basis of direct experimental results.